Light has a number of advantages as a stimulus to control molecular events; it has few off-target effects, it can be focused with subcellular resolution, and it can be rapidly modulated. Several technologies have been developed recently that use light-sensitive proteins to control electrical activity, cyclic AMP production and activation of G-protein coupled receptors in mammalian cells. However, although these technologies have revolutionized our study of these processes, they are not easily applied to the study of the majority of signal transduction cascades that depend on protein-protein interactions for function.
Cellular signaling pathways are part of a complex system of communication that governs basic cellular activities and coordinates cell actions. The ability of cells to perceive and correctly respond to their microenvironment is the basis of development, tissue repair, and immunity as well as normal tissue homeostasis. Errors in cellular information processing may be responsible for diseases such as cancer, autoimmunity, and diabetes. Understanding and manipulating cellular signaling pathways can provide mechanisms for drug screening assays, and for an understanding of important disease processes.
Signaling pathways, or signal transduction pathways, are often dependent upon an initial binding event, for example between a ligand and a cell-surface or cytoplasmic receptor, followed by protein-protein interactions in a network. In many examples, the initial binding event or the proximity of two interacting proteins in a pathway is sufficient to produce a biological effect of interest. Often, the behavior of a chain of interacting cellular proteins is altered following receptor activation. Research in signaling pathways may involve studying the spatial and temporal dynamics of receptors, and the components of signaling pathways that are activated by receptors, in various cell types.
Complex multi-component signal transduction pathways provide opportunities for feedback, signal amplification, and interactions inside one cell between multiple signals and signaling pathways. These systems are important in determining the biological effect of a perturbation, such a candidate drug or therapeutic modality. Indeed, pharmaceutical drug discovery, a multi-billion dollar industry, involves the identification and validation of therapeutic targets, as well as the identification and optimization of lead compounds. Desirable compound screening methods need to allow for both high throughput so that many individual compounds can be tested; and to provide biologically relevant information so that there is a good correlation between the information generated by the screening assay and the pharmaceutical effectiveness of the compound.
The development of screening assays and methods of easily manipulating protein interactions can provide better, faster and more efficient prediction of mechanisms of action, cellular effects and clinical drug performance. This issue is of great interest in a number of fields, and is addressed in the present invention.